AAS 201st Meeting, January, 2003
Session 20. Star Formation I
Poster, Monday, January 6, 2003, 9:20am-6:30pm, Exhibit Hall AB

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[20.17] Astrophysics of Young Star Binaries

L. Prato (UCLA), T. P. Greene (NASA/Ames), M. Simon (SUNY Stony Brook)

We describe our study of the astrophysics of individual components in close pre-main-sequence binaries. We observed both stars in systems located in 4 nearby star forming regions using low-resolution (R=760), infrared spectroscopy and photometry. For most components we detected photospheric absorption lines and were able to determine spectral type, extinction, K-band excess, and luminosity. A number of objects displayed featureless or pure emission line spectra. In ~50 % of the systems, the extinction and K-band excess of the primary stars dominate those of the secondaries. Masses and ages were determined for objects by placing them on the H-R diagram, overlaid with theoretical pre-main-sequence tracks. Most of the binaries appear to be coeval. The ages span 5\times105 to 1\times107 years. The derived masses range from the substellar, 0.06 M\odot, to 2.5 M\odot, and the mass ratios from M2/M1=0.04 to 1.0. About half of the sample shows evidence for circumstellar disks. The K-band excess is well correlated with the K-L color for stars with circumstellar material.

Partial support for this work was provided by NSF grants AST 98-19694 and AST 02-05427 (to M. S.).

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